Biology subjects

Muthaiyan Shanmugam, M.

Publications and source records attributed to Muthaiyan Shanmugam, M..

4 recordsLinked to original sources

bioRxiv2022

Methylglyoxal-derived hydroimidazolone, MG-H1, increases food intake by altering tyramine signaling via the GATA transcription factor ELT-3 in Caenorhabditis elegans

The Maillard reaction, a chemical reaction between amino acids and sugars, is exploited to produce flavorful food almost everywhere, from the baking industry to our everyday life. However, the Maillard reaction also takes place in all cells, from prokaryotes to eukaryotes, leading to the formation of Advanced Glycation End-products (AGEs). AGEs are a heterogeneous group of compounds resulting from the irreversible reaction between biomolecules and -dicarbonyls (-DCs), including methylglyoxal (MGO), an unavoidable byproduct of anaerobic glycolysis and lipid peroxidation. We previously demonstrated that Caenorhabditis elegans mutants lacking the glod-4 glyoxalase enzyme displayed enhanced accumulation of -DCs, reduced lifespan, increased neuronal damage, and touch hypersensitivity. Here, we demonstrate that glod-4 mutation increased food intake and identify that MGO-derived hydroimidazolone, MG-H1, is a mediator of the observed increase in food intake. RNA-seq analysis in glod-4 knockdown worms identified upregulation of several neurotransmitters and feeding genes. Suppressor screening of the overfeeding phenotype identified the tdc-1-tyramine-tyra-2/ser-2 signaling as an essential pathway mediating AGEs (MG-H1) induced feeding in glod-4 mutants. We also identified the elt-3 GATA transcription factor as an essential upstream factor for increased feeding upon accumulation of AGEs by partially regulating the expression of tdc-1 and tyra-2 genes. Further, the lack of either tdc-1 or tyra-2/ser-2 receptors suppresses the reduced lifespan and rescues neuronal damage observed in glod-4 mutants. Thus, in C. elegans, we identified an elt-3 regulated tyramine-dependent pathway mediating the toxic effects of MGO and associated AGEs. Understanding this signaling pathway is essential to modulate hedonistic overfeeding behavior observed in modern AGEs rich diets.

genetics↗

bioRxiv2019

Characterization of TAG-63 and its role on axonal transport in C. elegans

Model organisms are increasingly used to study and understand how neurofilament (NF)-based neurological diseases develop. However, whether a NF homolog exists in C. elegans remains unclear. We characterize TAG-63 as a NF-like protein with sequence homologies to human NEFH carrying various coiled coils as well as clustered phosphorylation sites. TAG-63 also exhibits features of NFL such as a molecular weight of around 70 kD, the lack of KSP repeats and the ability to form 10 nm filamentous structures in transmission electron micrographs. An anti-NEFH antibody detects a band at the predicted molecular weight of TAG-63 in Western blots of whole worm lysates and this band cannot be detected in tag-63 knockout worms. A transcriptional tag-63 reporter expresses in a broad range of neurons, and various anti-NFH antibodies stain worm neurons with an overlapping expression of axonal vesicle transporter UNC-104(KIF1A). Cultured neurons grow shorter axons when incubating with drugs known to disintegrate the NF network and rhodamine-labeled in vitro reconstituted TAG-63 filaments disintegrate upon drug exposure. Speeds of UNC-104 motors are diminished in tag-63 mutant worms with visibly increased accumulations of motors along axons. UNC-104/TAG-63 and SNB-1/TAG-63 not only co-localize in neurons but also revealed positive BiFC (bimolecular fluorescence assay) signals.

cell biology↗

bioRxiv2019

Depletion of intermediate filament IFB-1 negatively affects mobility and physiological function of mitochondria in C. elegans sensory neurons

Mitochondria and intermediate filament (IF) accumulations often occur during imbalanced axonal transport leading to various types of neurological diseases. It is still poorly understood whether a link between neuronal IFs and mitochondrial mobility exist. In C. elegans, among the 11 cytoplasmic IF family proteins, IFB-1 is of particular interest as it is expressed in a subset of sensory neurons. Depletion of IFB-1 leads to mild dye-filling and significant chemotaxis defects as well as reduced life span. Sensory neuron development is affected and mitochondria transport is slowed down leading to reduced densities of these organelles. Mitochondria tend to cluster in neurons of IFB-1 mutants likely dependent on fission but independent of fusion events. Oxygen consumption and mitochondrial membrane potential is measurably reduced in worms carrying mutations in the ifb-1 gene. Membrane potential also seems to play a role in transport such as FCCP treatment led to increased directional switching of mitochondria. Mitochondria colocalize with IFB-1 in worm neurons and appear in a complex with IFB-1 in pull-down assays. In summary, we propose a model in which neuronal intermediate filaments may serve as critical (transient) anchor points for mitochondria during their long-range transport in neurons for steady and balanced transport. Abstract Figure O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=117 SRC="FIGDIR/small/723205v3_ufig1.gif" ALT="Figure 1"> View larger version (32K): org.highwire.dtl.DTLVardef@1c6fc73org.highwire.dtl.DTLVardef@e7fd9aorg.highwire.dtl.DTLVardef@ba9742org.highwire.dtl.DTLVardef@20a9ed_HPS_FORMAT_FIGEXP M_FIG C_FIG SynopsisVarious neurological diseases are both associated with abnormal accumulations of neuronal intermediate filaments as well as mitochondria. Here, we report a link between these two phenomena employing the model organisms C. elegans. Depletion of neuronal intermediate filament IFB-1 impairs the transport of mitochondria in sensory neurons leading to clustered and accumulated mitochondria affecting neuronal growth and oxygen consumption in nematodes.

cell biology↗

bioRxiv2019

PTP-3(LAR PTPR) promotes intramolecular folding of SYD-2(liprin-α) to inactivate UNC-104(KIF1A) in neurons

This study aims to demonstrate how PTP-3 regulates SYD-2 to control UNC-104-mediated axonal transport. UNC-104 is the C. elegans homolog of kinesin-3 KIF-1A known for its fast shuttling of STVs (synaptic vesicle protein transport vesicles) in axons. SYD-2 is the homolog of liprin- in C. elegans known to directly regulate UNC-104 as well as being a substrate of LAR PTPR (leukocyte common antigen-related (LAR) protein tyrosine phosphatase (PTP) transmembrane receptor) with PTP-3 as the closest homolog in C. elegans. CoIP assays revealed increased interaction between UNC-104 and SYD-2 in lysates from ptp-3 knockout worms. Intramolecular FRET analysis revealed that SYD-2 predominantly exists in an open conformation state in ptp-3 mutants. These assays also revealed that non-phosphorylatable SYD-2 (Y741F) exists predominately in folded conformations while phosphomimicking SYD-2 (Y741E) exists predominantly in open conformations. In ptp-3 mutants, SNB-1 cargo accumulates in soma while at the same time UNC-104 motors increasingly cluster along initial segments of axons. Interestingly, the unc-104 gene is downregulated in ptp-3 mutants that might explain the vesicle retention phenotype. More strikingly, the few visibly moving motors and STVs were overly active in neurons of these mutants. We propose a model in which the lack of PTP-3 promotes increased open conformations of SYD-2 that in turn facilitates UNC-104/SYD-2 interactions boosting motor and STVs moving speeds.

cell biology↗